Graphic systems which operate on generalized computer platforms present graphic-related signals to peripheral devices such as cathode ray tube (CRT) display devices, printer/plotters, typically modularize the system software, wherein the basic graphic system communicates to one or more peripheral graphics devices through selected graphic device drivers, and may incude a plurality of drivers each customized for the particular peripheral device.
The display drivers access the stored image, either in bit-mapped format or vector display format and present to the peripheral device a particular subset of the entire object space. Although the entire object space may contain a plurality of object images, a particular area of interest may contain a small portion of the total number of objects present in the entire object space, wherein the display of the area of interest requires only the object(s) within the area of interest to be displayed, the remaining objects being omitted from the display.
While analogous processes for specifying an object in bit-mapped display systems, an object in a vector display typically is composed of a plurality of line drawing vectors, wherein a begin and end point are specified. A complete display of all edges and/or surfaces includes a list of the vectors. Present vector-driven display devices require a list of vectors (vector display list) which is stored in a memory space sufficient in size to contain the entire image stored in the entire object space, from which the objects displayed in a selected area of interest are selected. Typically, however, the object-related vectors are not organized or identified according to a format which can be readily identified by the display driver, or which can facilitate rapid object identification or detection, requiring the display driver to search the entire display list and provide individual point comparisons to recover the object(s) within the object space, imposing a speed penalty in the display of image within the area of interest.
Furthermore, the problem is exacerbated when element deletion is implemented by overwriting the image with an identical blank or black image, providing a redundant and complemetary image vectors, both of which must be identified to provide the correct current image. Thus, previous display drivers have required a time consuming vector-by-vector comparison of the entire display list to determine which vectors or objects will be displayed prior to the actual display on selected peripheral device. Alternately, annoying flicker is created during display as deleted objects first appear and become overwritten by blank or black vectors, which are simply "displayed" along with the visible vectors and objects to be deleted. Moreover, such deleted vectors or objects cause holes to appear in other, overlapping or overlapped objects.